Islands

How it works

What you get from it

A puzzle of small certainties. A 1 is an island on its own, so its neighbours are sea. A square that touches two different numbers is sea too. Each square you settle makes the next one easier to see.

It trains seeing the whole board. The sea has to stay in one piece, so a square that looks harmless can cut it in two.

Easy is a 6×6 with islands of up to 6 squares. Hard is a 10×10 with islands of up to 9.

Rules

A square grid with a number from 1 to 9 in some squares. Every number is the start of an island: a group of squares joined side to side, as many as the number says. Each island holds exactly one number.

Every square that is not on an island is sea. All the sea joins up side to side. No 2×2 block of it is sea. Exactly one shading fits.

How to play in Rather

Tap a square for sea. Tap again for a dot, a square you know is island. Tap a third time to clear it. The dots are your own notes.

Drag along a row or column to give every square on that line that matches the square you started on the same new mark. A tap or a drag is one Undo step.

A number dims once its island has exactly that many squares and is closed in by sea or the edge. It counts squares without checking them.

Numbered squares take no marks.

Where to start

Start with the 1s. Each is an island on its own, so every square beside it is sea.

Look for squares between two numbers. A square that touches two different islands would join them, so it is sea.

When an island has all its squares, ring it with sea. When it can only grow one way, grow it there.

Watch for pools. Three squares of sea in an L leave the fourth to be island, since a 2×2 of sea is not allowed.

Squares no number can reach are sea. Count how far each island could stretch.

Keep the sea in one piece. A square that would cut it in two has to be island.

When you’re stuck

Tap Hint. If sea or a dot is wrong, it clears it: “This one doesn’t fit.” Otherwise it marks what one technique settles, sea or dots. It says why: “This island has all its squares.”

The squares it reads are outlined. The squares it marks glow once.

Errors marks sea on a square that belongs to an island and a dot on a square that is sea.

Undo takes back a whole tap or drag at a time.

Sizes

• Easy 6×6 Islands of up to 6 squares.
• Medium 8×8 Islands of up to 8 squares.
• Hard 10×10 Islands of up to 9 squares.

Questions

Do I have to mark the dots?

No. They are your own notes. The puzzle is solved when the sea is exactly right, whether the island squares hold dots or nothing.

Can two islands touch?

Only at a corner. Two island squares side by side belong to one island, which holds one number.

Is there only one answer?

Yes. Every puzzle has exactly one shading that fits. The hint follows it.